Rubber goods such as tire treads often are made from elastomeric compositions that contain one or more reinforcing materials such as, for example, particulate carbon black and silica; see, e.g., The Vanderbilt Rubber Handbook, 13th ed. (1990), pp. 603-04.
Typically, filler(s), elastomeric material(s), and additives are chosen so as to provide a composition from which can be made rubber articles with an acceptable compromise or balance of performance properties such as traction, abrasion resistance, hysteresis, etc. Ensuring that reinforcing filler(s) are well dispersed throughout the elastomeric material(s) both enhances processability and acts to improve physical properties. Dispersion of fillers can be improved by increasing their interaction with the elastomer(s). Examples of efforts of this type include high temperature mixing in the presence of selectively reactive promoters, surface oxidation of compounding materials, surface grafting, and chemical modifications to the terminal ends of the polymers.
Chemical modification or functionalization of the polymers to increase interactivity between the polymer and the particulate filler(s) also can counteract the tendency of filler particles to agglomerate. Dissociation of such agglomerates can negatively impact physical properties of articles made from filled compositions; thus, reduction of the tendency of filler particles to agglomerate also is desirable.
Use of compositions that employ more than one type of particulate filler is growing. Functionalized polymers, i.e., polymers that include one or more functional groups (typically terminal functionality), interact differently with different fillers. Adequate interactivity often is sought by blending two or more differently functionalized polymers, an that approach assumes that functional groups that interact with a particular filler will exhibit the same or similar interactivity in a mixed filler system. Some have attempted to provide multiple functionalities in a single reaction scheme; see, e.g., U.S. patent publ. no. 2006/0135701 A1 which teaches a sequential functionalization-termination process whereby multiple functional groups can be attached to the same polymer chain.
Where an elastomer is made by anionic polymerization techniques, attachment of certain functional groups is difficult due to the fact that carbanions, such as living polymers, are terminated by active hydrogen atoms present in, e.g., primary and secondary amine groups. However, amine functional groups provide desirable interaction with particulate fillers, particularly carbon black, so commercially useful methods of providing living polymers with amine functionality remain desirable. Because interactivity with fillers tends to increase as the number of hydrogens bonded to the amino nitrogen increases, the provision of secondary and primary amine-functionalized polymers is particularly desirable.
One procedure for providing amine functionality to anionically initiated polymers is described by K. Ueda et al., “Synthesis of Polymers with Amino End Groups-3. Reactions of Anionic Living Polymers with α-Halo-ω-aminoalkanes with a Protected Amino Functionality,” Macromolecules, 1990, 23, 939-45. Anionic living polystyrene is reacted with an α-halo-ω-aminoalkane followed by de-protection of the trialkylsilyl-protected amine functionality to provide a primary amino-functionalized polystyrene. The academic laboratory conditions employed limit the utility of this procedure, however, a fact recognized by other academic publications; see, e.g., R. Quirk et al., “Anionic Synthesis of ω-Dimethylamino-Functionalized Polymers by Functionalization of Polymeric Organolithiums with 3-Dimethylaminopropyl Chloride,” Polym. Int., 1999, 48, 99-108.